The SCR of NO by NH3 was studied with hybrid catalysts, in which an oxidation component (Mn-Cu or Ce-Zr mixed oxides) and SCR catalysts of different activities in fast SCR (Fe-ZSM-5 of different Fe content and H-ZSM-5) are combined in physical mixtures. Fast SCR, which is SCR of NO2/NO mixtures, is believed to be the final step of the reaction mechanism causing the synergy and being initiated by NO2 formation over the oxidation component. In our studies, no correlation between fast-SCR activity of the SCR component and the performance of the hybrid was observed. In addition, a hybrid catalyst was found that provided rates of standard SCR significantly exceeding rates in fast SCR achieved by the SCR component alone in a wide temperature range. Therefore, fast SCR is not part of the reaction sequence causing the drastic synergetic effects between the components. (C) 2016 Elsevier B.V. All rights reserved.